This invention generally relates to the art of optical fibers and, particularly, to a fiber optic apparatus and method for cross-connecting the individual optical fibers of a plurality of fiber optic ribbons.
Fiber optic circuitry is increasingly being used in electronics systems where circuit density is ever-increasing and is difficult to provide with known electrically wired circuitry. An optical fiber circuit is formed by a plurality of optical fibers carried by a dielectric, and the ends of the fibers are interconnected to various forms of connectors or other optical transmission devices. A fiber optic circuit may range from a simple cable which includes a plurality of optical fibers surrounded by an outer cladding or tubular dielectric to a more sophisticated optical backplane or flat fiber optic circuit formed by a plurality of optical fibers mounted on a substrate in a given pattern or circuit geometry.
One type of optical fiber circuit is produced in a ribbonized configuration wherein a row of optical fibers are disposed in a side-by-side parallel array and coated with a matrix to hold the fibers in the ribbonized configuration. This often is called xe2x80x9cribbonizingxe2x80x9d In the United States, an eight-fiber ribbon or a twelve-fiber ribbon have become common. In other foreign countries, the standard may range from as a low as four to as high as twenty-four fibers per ribbon. Multi-fiber ribbons and connectors have a wide range of applications in fiber optic communication systems. For instance, optical splitters, optical switches, routers, combiners and other systems have input fiber optic ribbons and output fiber optic ribbons.
With various applications such as those described above, the individual optical fibers of input fiber optic ribbons and output fiber optic ribbons are cross-connected or reorganized whereby the individual optical fibers of a single input ribbon may be separated and reorganized into multiple or different output ribbons. The individual optical fibers are cross-connected or reorganized in what has been called a xe2x80x9cmixing zonexe2x80x9d between the input and output ribbons.
Optical backplanes are fabricated in a variety of manners, ranging from laying the optical fibers on a substrate by hand to routing the optical fibers in a given pattern or circuit geometry onto the substrate by mechanized apparatus. The individual optical fibers are cross-connected or reorganized on the substrate between input and output ribbons projecting from input and output ends or edges of the substrate. Therefore, the above-mentioned xe2x80x9cmixing zonexe2x80x9d is provided by the substrate, itself. The input and/or output ribbons which project from the edges of the substrate then are cut-off at predetermined lengths according to the backplane specifications and are terminated to a plurality of fiber optic connectors.
With cross-connecting apparatus as described above, it is important that the individual optical fibers of any particular fiber optic ribbon be in a predetermined sequence. In other words, it is important than an operator be able to know which tiny individual fiber of each ribbon is the xe2x80x9c1xe2x80x9d or the xe2x80x9c8xe2x80x9d fiber within the ribbon with the fibers hypothetically numbered from one side or edge of the ribbon sequentially to the opposite or edge of the ribbon. This is important in terminating the ribbons to the fiber optic connectors, as described above. The connector typically tells an operator where the xe2x80x9c#1xe2x80x9d and/or the xe2x80x9c#8xe2x80x9d fiber is to be inserted into the connector. Typically, the fiber optic ribbons are cut-off immediately before termination of the ribbons in the connectors. If one of the tiny individual fibers is out of sequence, the circuit scheme of the connector is destroyed and, once the fibers are permanently fixed within the connector, the entire cross-connecting apparatus or harness must be discarded and wasted.
Heretofore, fiber-orientation inspections or testings have been made to assure that the fiber sequence is accurate before termination procedures are initiated. One verification system is to manually/visually trace each fiber throughout its entire length as routed along the apparatus. This system is time consuming, inefficient and still subject to human error. A second verification system is to perform optical tests after the fiber optic ribbons are terminated in the connectors. These tests are accurate, but they are conducted after termination and, as stated above, entire apparatus or optical harnesses may have to be discarded at considerable expense if a test reveals a mis-routed fiber or fibers. The present invention is directed to solving these problems by an extremely simple system for cutting the individual optical fibers of the fiber optic ribbons at different lengths in a predetermined pattern correlated to the predetermined sequence of the fibers in the ribbon(s).
An object, therefore, of the invention is to provide a fiber optic apparatus for cross-connecting the individual optical fibers of a plurality of fiber optic ribbons, the apparatus being fabricated by a method of verifying a predetermined fiber pattern or sequence.
In the exemplary embodiment of the invention, a plurality of individual optical fibers are routed on a flat substrate to form at least one first fiber optic ribbon leading onto the substrate and at least one second fiber optic ribbon leading away from the substrate to a terminating end of the ribbon. The individual optical fibers of at least the second fiber optic ribbon are routed in a predetermined sequence from one side or edge of the ribbon to an opposite side or edge thereof. The individual optical fibers at the terminating end of the second fiber optic ribbon are cut-off at different lengths in a predetermined pattern correlated to the predetermined sequence of fibers, in order to visually identify any fiber which is out of the predetermined sequence.
The invention contemplates that the individual optical fibers of both the first and second fiber optic ribbons be routed in a predetermined sequence, and the individual fibers of each fiber optic ribbon are cut-off at terminating ends thereof in predetermined patterns of different lengths. As disclosed herein, the individual optical fibers are routed onto and off of the substrate to form a plurality of the first fiber optic ribbons and a plurality of the second fiber optic ribbons. All of the ribbons may be cut-off in predetermined patterns with the individual fibers at different lengths.
According to one aspect of the invention, the individual optical fibers at the terminating end of any ribbon are cut-off at progressively different lengths from one side of the ribbon to an opposite side thereof. This creates a xe2x80x9cwedgexe2x80x9d shaped pattern which makes it very simple and easy for an operator to visually ascertain if any of the individual optical fibers are out of their predetermined sequence.
The invention also contemplates a method of fabricating the fiber optic apparatus descried above, including the termination of the fiber optic ribbons to appropriate fiber optic connectors, after the ribbons are trimmed or cut for termination purposes.